Emulated Numpad Mapping - Numpad Period?
In emulated numpad mode there isn't a non-numpad key that's mapped to the same functions as numpad period.  The way to get a key to do what numpad period does is to map your own choice of key to do the same things as numpad period does.  Numpad period is mapped to "View Selected" in eight or more windows (you can find them by searching for key-bindings for 'numpad' and scanning through the results but searching for 'numpad .' doesn't work).  The window in which I use numpad period most often is the 3D view.  Below is an explanation of how to remap the numpad period key in that window. A similar process would work for any other window type you want to remap.

I used this explanation to change the key binding in user preferences (Ctrl+Alt+U) for the View selected command under 3D View> 3D View (Global)> View Selected (see below, I have mapped it to semicolon ;).



Before you pick the key to map it to, you might like to make sure that your new binding isn't used for some other command. You can search by key by changing Name in the top search bar to Key-Binding and enter the key you'd like to check.  If nothing shows up (see screenshot) then you're safe; if some bindings show up you might still be ok if none are applicable to the 3D view.



Rather annoyingly, searching for 'period' . doesn't find the bindings to numpad period - not even if you type the period with a numpad - but you can get close by searching for the key-bindings for 'numpad' (type in the word as though it was a key).

If you feel adventurous, you might prefer to add an additional binding rather than removing the numpad binding (maybe you'll buy a numpad one day). To do that, take a look at the command you would have remapped by clicking the little white triangle:



That shows the command is view3d.view_selected.  Scroll way down to the end of the list of bindings and find the Add New button. Press it and you'll get a new binding called none just above the button you clicked:



Expand the key binding, enter the command and set the key you want bound to it:

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Finally, don't forget to save your user preferences!